When a cat eliminates warm fecal matter into a litter box or cat waste elimination system, warm, odor laden air rises from it in the first 5 to 10 minutes of the animal's excretion before a crust forms on the outer shell of the fecal matter. The device of this invention is designed to minimize the amount of this odor-laden air that leaves the box and circulates into the general air in the room in which the box is placed.